Lessons are beginning to emerge from Terri Schiavo’s fight over food and water. The country has joined her in a crash-course in Florida law and medical ethics, and people are looking for the answer to the final essay question: how can I keep this from happening to me?

Monday’s edition of the Miami Herald detailed an increasingly common answer to that question—the living will. According to the Herald, the non-profit group Aging With Dignity has taken requests for 20,000 copies (200 was the weekly average) of its living will template since October 16. As group president, Paul Malley, surmised, "[i]f there’s anything good that can come of this tragedy, it is [the proven need for a living will]. She is teaching us a lot."

Indeed, Terri is teaching us a lot. But is the living will what we really need to learn? Is "put it in writing" really the moral of Terri’s story?

Many attorneys and bioethicists think so. "If you don’t want your loved ones fighting at your deathbed, make sure they all know what you want and what you don’t want," says Ken Goodman, director of the University of Miami ethics program. Attorney Paul Stokes offers still more advice: draft a will and "[t]hen send a copy to your doctor, to the hospital… make photocopies and give them to your friends and relatives."

But before you slip your living will and testament inside this year’s Christmas cards, there are a few things to consider.

First, contrary to the assurances of Mr. Goodman, a living will does not guarantee that your family won’t still be fighting over your feeding tubes. While a carefully crafted living will can offer relatives and doctors some guidance on what kinds of care you do and do not want, it certainly cannot ensure that members of your family will agree on how to give or withhold that care.

Studies have shown that even when there is a living will, doctors will ordinarily consult families on the sort of treatment to be given. They will assume, despite the document before them, that the family knows the patient and her preferences best, and will often not make life-and-death decisions without extensive family consultation. Thus, the Schindlers and Schiavos might still have argued over the measure of care to be given even if Terri had jotted down her preferences.

Why? Because living wills are fairly complicated and difficult documents to craft, and often even harder to interpret. Notwithstanding the well-meaning attempts of Aging With Dignity and other organizations to simplify and democratize the process, living wills and advance directives suffer from the intrinsic limitations of their draftsmen and the nature of the beast they are trying to tame.

Crafting a living will requires people to know what they want, when they want it, and how they want to get it. There is some evidence to suggest that answers to these questions are not easy to come by—even when we stop to think about them. Heck, hand me a remote control and I can’t decide which games I want to watch with my NFL Sunday Ticket, and I’m supposed to tell you which tubes, plugs and wires I want pulled when? Ask me on Sunday and you can unplug anything but the TV and the refrigerator.

As one group of scholars has described the drafting process, "[p]eople preparing living wills not only make imponderable medical choices, they make them for a hypothetical world. They imagine what they would want in an unspecifiable future confronted with unidentifiable medical conditions with unpredictable treatments." Such hypothesis erects a natural barrier to clarity and often creates either an over-generalized directive that discusses neither particular medical situations the patient may experience, nor the particular treatments the patient may want; or else an over-specific directive that in turn is insufficiently general to accommodate an unforeseen condition or treatment. Both will often require a spectacular amount of interpretation on the part of the family and physician as they seek to divine the patient’s intentions.

Of course, even if we could resolve all of our own intentions, articulate them in clear and unflappable terms, having seen like the prophets both our future condition and the balms available, we must still contend with one of life’s true constants—change. Remarkably enough, our thoughts on the subjects of infirmity and death, and the meaning and quality of life, are prone to change over time, and likely without our noticing. When researchers asked people whether they thought their preferences for life-sustaining treatment had changed over just a two-year period, only 20% of those patients whose preferences had indeed changed recognized that they had. Another study found that decisions fluctuated substantially during the study’s 2-year period, with "only 18-43% of the patients who had said they wanted a particular treatment at the beginning of the study saying that they wanted it at the end."

The fact is most of us will find it hard to determine what kinds of treatment we want and under what conditions we want them. And once those determinations are made and written down with the kind of vague-specificity that only a lawyer could love, there remains the high probability that those determinations will evolve over even short periods of time casting a pall of suspicion over our finely penned intentions. All of this is not to say, of course, that we ought not to discuss these matters with our closest friends and loved ones. Those discussions, like living wills, can be instructive. It is simply to suggest that the current renaissance of the living will must be tempered. It is unlikely to relieve us from the complex burdens of end of life choices, and is far from a cure for the family feud.

As I have said regarding more than one of my wife’s grocery lists, just because you put it in writing doesn’t always mean I know what you said.

Nathaniel Stewart is an Adjunct Fellow at the John M. Ashbrook Center for Public Affairs at Ashland University, and a contributor to the Encyclopedia of Bioethics 3d. ed.